RcsAB is a major repressor of Yersinia biofilm development through directly acting on hmsCDE, hmsT and hmsHFRS

Nan Fang,Dongsheng Zhou,Li Wang,Yiquan Zhang,Huiying Yang,Lei Liu,Yanping Han,Ruifu Yang,Haihong Fang

doi:10.1038/srep09566

Abstract

Biofilm formation in flea gut is important for flea-borne transmission of Yersinia pestis. There are enhancing factors (HmsHFRS, HmsCDE, and HmsT) and inhibiting one (HmsP) for Yersinia pestis biofilm formation. The RcsAB regulatory complex acts as a repressor of Yesinia biofilm formation, and adaptive pseudogenization of rcsA promotes Y. pestis to evolve the ability of biofilm formation in fleas. In this study, we constructed a set of isogenic strains of Y. pestis biovar Microtus, namely WT (RscB+ and RcsA-), c-rcsA (RscB+ and RcsA+), ΔrcsB (RscB- and RcsA-), and ΔrcsB/c-rcsA (RscB- and RcsA+). The phenotypic assays confirmed that RcsB alone (but not RcsA alone) had an inhibiting effect on biofilm/c-di-GMP production whereas assistance of RcsA to RcsB greatly enhanced this inhibiting effect. Further gene regulation experiments showed that RcsB in assistance of RcsA tightly bound to corresponding promoter-proximal regions to achieve transcriptional repression of hmsCDE, hmsT and hmsHFRS and, meanwhile, RcsAB positively regulated hmsP most likely in an indirect manner. Data presented here disclose that pseudogenization of rcsA leads to dramatic remodeling of RcsAB-dependent hms gene expression between Y. pestis and its progenitor Y. pseudotuberculosis, enabling potent production of Y. pestis biofilms in fleas.

Highlights

RcsAB is a major repressor of Yersinia biofilm development through directly acting on hmsCDE, hmsT, and hmsHFRS
RcsAB box-like sequences could be found within the promoterproximal regions of hmsCDE, hmsT and hmsHFRS, indicating that they might serve as direct RcsAB targets (Table S3), which promoted us to elucidate RcsAB-dependent expression of these candidate genes. hmsP was included in the following gene regulation analyses
Transcriptional repression of genes for biofilm exopolysaccharide biosynthesis by RcsB with assistance of its auxiliary protein RcsA has been characterized in several bacterial species (Table S1)

Summary

Introduction

RcsAB is a major repressor of Yersinia biofilm development through directly acting on hmsCDE, hmsT, and hmsHFRS. Biofilm formation in flea gut is important for flea-borne transmission of Yersinia pestis. There are enhancing factors (HmsHFRS, HmsCDE, and HmsT) and inhibiting one (HmsP) for Yersinia pestis biofilm formation. The RcsAB regulatory complex acts as a repressor of Yesinia biofilm formation, and adaptive pseudogenization of rcsA promotes Y. pestis to evolve the ability of biofilm formation in fleas. Further gene regulation experiments showed that RcsB in assistance of RcsA tightly bound to corresponding promoter-proximal regions to achieve transcriptional repression of hmsCDE, hmsT and hmsHFRS and, RcsAB positively regulated hmsP most likely in an indirect manner. Formation of attached Y. pestis biofilms in flea gut is important for flea-borne transmission of this pathogen[1,2,3]

Methods

Results

Conclusion